Devices for preventing inadvertent movement of automobiles are well known. They are most frequently used when changing tires, either to replace a flat tire or when rotating tires to provide for even wear.
Probably the oldest, simplest and still most widely used device of this type is a simple triangular solid. When needed, it is wedged between the tire and the ground on the downhill side of a tire that is remote from the tire being removed and then the opposite end of the vehicle is raised on a jack. In many, if not most, situations such a wedge performs adequately, however, there are a significant number of occasions when it does not. For example, the simple triangular block has a tendency, when on an incline, to move away from the tire. It also has a tendency to be pushed by the wheel, thereby permitting some movement of the vehicle. Since the jacks normally furnished with autombiles are rather easily upset, it is important to prevent even small movement of the vehicle. In view of the dire consequences that are likely to ensue when the simple triangular solid does not function properly, even a relatively small percentage of such failures represents a severe drawback.
A number of devices have been designed with an eye toward overcoming the disadvantages of the simple triangular solid chock. Included among those are the devices covered by U.S. Pat. Nos. 3,297,111, 2,299,115, 2,797,774 and 1,894,439. Each of these, while representing in one respect or another an improvement over the basic triangular chock, still has certain disadvantages which render it not entirely satisfactory.